Vigilance against predators induced by eavesdropping on heterospecific alarm calls in a non-vocal lizard Oplurus cuvieri cuvieri (Reptilia: Iguania)

Prey animals can reduce their risk of predation by detecting potential predators before encounters occur. Some animals gain information about nearby predators by eavesdropping on heterospecific alarm calls. Despite having well-developed ears, most lizards do not use vocal information for intraspecific communication, and few studies have shown practical use of the ears in wild lizards. Here, we show that the Madagascan spiny-tailed iguana (Oplurus cuvieri cuvieri) obtains auditory signals for predator detection. The Madagascan spiny-tailed iguana and the Madagascar paradise flycatcher (Terpsiphone mutata) are syntopic inhabitants of the Ampijoroa dry deciduous forest of Madagascar. The iguana and the flycatcher have neither a predator–prey relationship nor resource competition, but they have shared predators such as raptors and snakes. Using playback experiments, we demonstrated that the iguana discriminates mobbing alarm calls of the flycatcher from its songs and then enhances its vigilance behaviour. Our results demonstrate the occurrence of an asymmetrical ecological relationship between the Madagascan spiny-tailed iguana and the paradise flycatcher through eavesdropping on information about the presence of predators. This implies that indirect interspecific interactions through information recognition may be more common than generally thought in an animal community.     

Synthesis and structure–activity relationships of N-aryl-piperidine derivatives as potent (partial) agonists for human histamine H3 receptor

4-((1H-Imidazol-4-yl)methyl)-1-aryl-piperazine and piperidine derivatives were designed and synthesized as candidate human histamine type 3 agonists. The piperazine derivatives were found to have low (or no) affinity for human histamine H3 receptor, whereas the piperidine derivatives showed moderate to high affinity, and their agonistic activity was greatly influenced by substituents on the aromatic ring. Among the piperidine-containing compounds, 17d and 17h were potent human histamine H3 receptor agonists with high selectivity over the closely related human H4 receptor. Our results indicate that appropriate conformational restriction, that is, by the piperidine spacer moiety, favors specific binding to the human histamine H3 receptor.     

Expression of epithelial calcium transport system in rat cochlea and vestibular labyrinth

Background  

The low luminal Ca²⁺ concentration of mammalian endolymph in the inner ear is required for normal hearing and balance. We recently reported the expression of mRNA for a Ca²⁺-absorptive transport system in primary cultures of semicircular canal duct (SCCD) epithelium.     

Palmitoylated Ras proteins traffic through recycling endosomes to the plasma membrane during exocytosis

Ras proteins regulate cell growth, death, and differentiation, and it is well established that this functional versatility is accomplished through their different subcellular localizations. Palmitoylated H- and N-Ras are believed to localize at the perinuclear Golgi and plasma membrane (PM). Notably, however, recycling endosomes (REs) also localize to a perinuclear region, which is often indistinguishable from the Golgi. In this study, we show that active palmitoylated Ras proteins mainly localize intracellularly at REs and that REs act as a way station along the post-Golgi exocytic pathway to the PM. H-Ras requires two palmitoyl groups for RE targeting. The lack of either or both palmitoyl groups leads to the mislocalization of the mutant proteins to the endoplasmic reticulum, Golgi apparatus, or the PM. Therefore, we demonstrate that palmitoylation directs Ras proteins to the correct intracellular organelles for trafficking and activity.     

Cytohesin-2/ARNO,through Its Interaction with Focal Adhesion Adaptor Protein Paxillin,Regulates Preadipocyte Migration via the Downstream Activation of Arf6

The formation of primitive adipose tissue is the initial process in adipose tissue development followed by the migration of preadipocytes into adipocyte clusters. Comparatively little is known about the molecular mechanism controlling preadipocyte migration. Here, we show that cytohesin-2, the guanine-nucleotide exchange factor for the Arf family GTP-binding proteins, regulates migration of mouse preadipocyte 3T3-L1 cells through Arf6. SecinH3, a specific inhibitor of the cytohesin family, markedly inhibits migration of 3T3-L1 cells. 3T3-L1 cells express cytohesin-2 and cytohesin-3, and knockdown of cytohesin-2 with its small interfering RNA effectively decreases cell migration. Cytohesin-2 preferentially acts upstream of Arf6 in this signaling pathway. Furthermore, we find that the focal adhesion protein paxillin forms a complex with cytohesin-2. Paxillin colocalizes with cytohesin-2 at the leading edges of migrating cells. This interaction is mediated by the LIM2 domain of paxillin and the isolated polybasic region of cytohesin-2. Importantly, migration is inhibited by expression of the constructs containing these regions. These results suggest that cytohesin-2, through a previously unexplored complex formation with paxillin, regulates preadipocyte migration and that paxillin plays a previously unknown role as a scaffold protein of Arf guanine-nucleotide exchange factor.     

Sex- and tissue-specific expression of P450 aromatase (cyp19a1a) in the yellowtail clownfish,Amphiprion clarkii

To investigate the role of estrogen in the gonad of yellowtail clownfish Amphiprion clarkii, we isolated cDNA encoding cytochrome P450 aromatase (Cyp19a1a) from the adult ovary. The full-length cDNA of clownfish cyp19a1a is 1928-bp long and encodes 520 amino acids. Real-time quantitative RT-PCR analysis showed that cyp19a1a was expressed mainly in the ovary of female-phase fish. In situ hybridization and immunohistochemical observations showed that positive signals were restricted to the ovarian follicle of the female-phase fish. In contrast, Cyp19a1a signal was not detected in the ambisexual gonad of the male-phase fish. These findings suggest that Cyp19a1a is involved in oogenesis in the female-phase fish, but not in the ambisexual gonad of male-phase fish.     

Characterization of multiple alternative forms of heterogeneous nuclear ribonucleoprotein K by phosphate-affinity electrophoresis

The phosphorylation of heterogeneous nuclear ribonucleoprotein K (hnRNP K) is thought to play an important role in cell regulation and signal transduction. However, the relationship between hnRNP K phosphorylation and cellular events has only been indirectly examined, and the phosphorylated forms of endogenous hnRNP K have not been biochemically characterized in detail. In this study, we extensively examined the phosphorylated forms of endogenous hnRNP K by direct protein-chemical characterization using phosphate-affinity electrophoresis followed by immunoblotting and MS. Phosphate-affinity electrophoresis enabled us to sensitively detect and separate the phosphorylated forms of hnRNP K. When we used 2-DE with phosphate-affinity SDS-PAGE in the second dimension, the nuclear fraction contained more than 20 spots of endogenous hnRNP K on the 2-D map. We determined that the multiple forms of hnRNP K were produced mainly by alternative splicing of the single hnRNP K gene and phosphorylation of Ser116 and/or Ser284. Furthermore, the subcellular localization of these proteins revealed by the 2-D gel correlated with their phosphorylation states and alternative splicing patterns. The results also indicated that the multiple forms of hnRNP K were differentially modulated in response to external stimulation with bacterial lipopolysaccharide or serum.     

A new model for predicting time course toxicity of heavy metals based on Biotic Ligand Model (BLM)

A new model for predicting time course toxicity of heavy metals was developed by extending the effective ratio of biotic ligand binding with toxic heavy metals to the total biotic ligand for 50% of test organisms (f₅₀) derived by the Biotic Ligand Model (BLM). BLM has been well-known as a useful model for prediction of heavy metal toxicity. BLM can consider the effect of exposure conditions such as pH and Ca²⁺ on heavy metal toxicity. In addition to the exposure conditions, heavy metal toxicity is strongly dependent on exposure time. In this study, BLM is extended to predict time dependency of heavy metal toxicity by connecting with the concept of primary reaction. The model developed in this study also generates the estimation of the 50% effect concentration (EC₅₀) for toxicologically unknown organisms and heavy metals. Two toxicological and kinetic constants, f_50,0 and k, were derived from the initial value of f₅₀ (f_50,0) and a time constant (k) independent of time. The model developed in this study enables us to acquire information on the toxicity of heavy metals such as Cu, Cd and Co easily.